Interfacing PIC16F877A with NEO-6M GPS module

This post shows how to interface the PIC16F877A microcontroller with GPS module in order to receive data from satellites where the GPS module used in this project is u-blox NEO-6M (other modules also should work). With the NEO-6M GPS module we can measure position (latitude, longitude and altitude), time (UTC), date, speed and some other data. — GPS: Global Positioning System —

In this project I’ll send information of latitude, longitude, altitude, time (UTC), date, speed and course serially (using serial port) to the laptop (PC). Data are sent to the laptop after receiving it from the GPS module. The laptop displays all data with serial monitor software such as Windows hyper terminal, Arduino serial monitor, CCS C IDE (C-Aware IDE) serial monitor …

The NEO-6M GPS module which I’m using is similar to the one shown below:

Generally the NEO-6M GPS module has 4 pins: VCC, RX, TX and GND. It uses serial communication (UART protocol) to communicate with the microcontroller where RX/TX pins are for receiving/transmitting data from/to the microcontroller.

GPS Library for CCS C compiler:
To simplify this project I wrote a small library for GPS modules, this library decodes (parses) GPS NMEA sentences (the GPS module serially sends NMEA sentences to the MCU, these sentences contain all data we need, but they need to be decoded). This library gets all data from 2 sentences: RMC ($GPRMC) and GGA ($GPGGA). — NMEA: National Marine Electronics Association —

The GPS library decodes the RMC sentence which gives latitude, longitude, time, date, speed and course. It also decodes the GGA sentence in order to get altitude and number of satellites used by the module.
$GPRMC: Recommended minimum specific GPS/Transit data
$GPGGA: Global Positioning System Fix Data

GPS Library for CCS C compiler can be downloaded from the link below, its full name is “GPS_Lib.c“:GPS Library download

To be able to send data from the microcontroller to the laptop we need a USB-to-Serial converter module. In this project I used the FT232RL module (FTDI232), other modules can be used including the Arduino boards.
The GND pin of the USB-to-Serial converter is connected to circuit ground and RX pin is connected to PIC16F877A TX (RC6) pin (pin #25).

In this project the PIC16F877A microcontroller runs with 8 MHz crystal oscillator.

Interfacing PIC16F877A with NEO-6M GPS module C code:
The C code below is for CCS C compiler, it was tested with version 5.051.

With the code below we can get the following data from the NEO-6M GPS module:
latitude, longitude, altitude, time (UTC), date , speed, course and number of satellites in use. The image below shows my result (I used Arduino IDE serial monitor):

I had already tried that for the record. I have solved the issue by removing changing line 50 from if(strcmp(sentence, “GPRMC”) == 0) to if(strcmp(sentence, GPRMC_ok) == 0), that appears to have resolved the issue